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05-10-2011, 08:16 PM   #1
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problem with K-X and K mount manual lens

First, please do not refer me to the sticky. I have read: https://www.pentaxforums.com/forums/pentax-dslr-discussion/93285-pentax-k-x-w...-old-lens.html
https://www.pentaxforums.com/forums/pentax-beginners-corner-q/59272-shooting-...x-dslrs-f.html
and the embedded link within.

I am a new K-X user and recently received my first manual focus lens. It is a Vivitar 28mm f2.8 (according to the Bestiary it is made by Komine and a K mount (13)). While I just may not be used to mounting these lenses, it does not feel like a stable mount. I have read several other blogs and have tried to unscrew the black base with the 3 screws and the extruding metal pin with 2 screws beneath it, neither of which has resulted in a secure fit, though each has felt more promising.

When I am able to fit it relatively snuggly, I notice that when I change the aperture the viewfinder gets darker, which I have read is not supposed to happen with K mount lenses until using the green button.

Thank you so much for your help in advance and I apologize if I have overlooked something obvious.

05-10-2011, 09:34 PM   #2
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QuoteOriginally posted by shinjitsu Quote
unscrew the black base with the 3 screws and the extruding metal pin with 2 screws beneath it,
I'm not exactly sure what you're referring to?

Anyway, I have (or had) the same exact Vivitar-Komine wide angle lens. My copy mounted snugly to my K-x; even felt tighter than the kit lens.

What you described (viewfinder dimming) seem to indicate the lens is actually stopping down with the aperture ring while the lens is mounted; it's not supposed to. Aperture should be wide-open all the time when mounted and only stopped down to your setting when taking a shot (or metering with green button).

If you operate the lens' spring loaded aperture lever manually by hand, does the aperture blades move?

Last edited by K57XR; 05-10-2011 at 09:40 PM.
05-10-2011, 09:35 PM   #3
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QuoteOriginally posted by shinjitsu Quote
...and the extruding metal pin with 2 screws beneath it, neither of which has resulted in a secure fit, though each has felt more promising.
That makes me think your lens is not a K mount at all, maybe something close though. Vivitars usually have some letter code identifying the mount type, maybe after the LENS MADE IN JAPAN text on or below the aperture ring. My K12 says "P/K" there.

A photo of the mount might help. These are tricky, especially because Vivitars tend to have a lot of super-reflective chrome. It is great practice for you. Try for as much detail as you can.
05-10-2011, 09:47 PM   #4
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I looked up the serial number and everything in the Bestiary and it said it was. The text after MADE IN JAPAN says K/AR.

When I move the lever by hand the aperture blades do not move. I will try to take pictures soon.

@K57XR, you were able to mount it without modifying the lens at all? Mine feels like there is an extra few millimeters.

05-10-2011, 10:16 PM   #5
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QuoteOriginally posted by shinjitsu Quote
The text after MADE IN JAPAN says K/AR
When I move the lever by hand the aperture blades do not move. I will try to take pictures soon.
If you set the aperture ring all the way to the highest number (i.e. fully stopped down), I believe 22, then move the lever, the blades still do not move? If they don't, that isn't good...sorry to say.

K/AR mount - That's a designation for KA mount with "A" setting on the aperture ring. The "R" means it also has the "Ricoh Pin". I have that version, too. And yes, the lens will (and should) mount without modifications.. Most, if not all, K-mount lenses will mount on all K-bodies without any modifications. Though, I came across a thread where a third party lens had a protruding flange at the base which had to be removed, but I don't think this applies to your Vivitar

As mentioned above, post a photo of the lens mount and maybe the letter designation on the side as well so we can get a better look....the black base you described is throwing me off?
05-10-2011, 10:32 PM   #6
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QuoteOriginally posted by K57XR Quote
...K/AR mount - That's a designation for KA mount with "A" setting on the aperture ring. The "R" means it also has the "Ricoh Pin". I have that version, too.
I think that might be a Konica mount. While Vivitar had a lot of different markings, what I'm used to seeing is "P/K", "P/K-A", or "P/K-A R-P/K", the last one with the Ricoh pin.

If you look at a K-mount, there are three tabs sticking out of the mount. On a Konica mount, it looks pretty similar, but one tab will have a rectangular notch cut into it, almost centered in a tab. Minolta mounts have a very similar notch, more offset.

Konica is kind of bad news, I'm afraid.
05-10-2011, 10:43 PM   #7
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Damn, I'm fairly certain I see the rectangular notch you describe.

Is there no way of using it on my K-X, even with modification?
05-11-2011, 03:55 AM   #8
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The problem you are going to have with a K/AR mount is that the flange focal distance is about 5 mm shorter than PK. This means that it is not possible to focus to infinity without an optical adapter, and AFAIK no such adapter exists. (There are adapters for Nikon F, Canon FD, and Minolta MD).

05-11-2011, 05:33 AM   #9
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QuoteOriginally posted by Just1MoreDave Quote
I think that might be a Konica mount. While Vivitar had a lot of different markings, what I'm used to seeing is "P/K", "P/K-A", or "P/K-A R-P/K", the last one with the Ricoh pin.
Konica is kind of bad news, I'm afraid.
Good call, Just1MoreDave. I stand corrected. I didn't think about the Konica mounts.

Edit: I just checked my Vivitar 28mm F2.8 and it is marked P-K/A R-P/K.

Last edited by K57XR; 05-11-2011 at 05:40 AM.
05-12-2011, 11:10 AM   #10
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QuoteOriginally posted by shinjitsu Quote
Damn, I'm fairly certain I see the rectangular notch you describe.

Is there no way of using it on my K-X, even with modification?
I have done this a couple of times and it's like running a marathon - an accomplishment, a lot of work but not a terribly practical way to cover 26.2 miles.

It might be possible but you have three major technical hurdles. One is shortening the lens 5mm. The second is retaining the aperture control. Third, finding a place to attach the new mount. It might work, because Vivitar had to do it to sell the lens in other versions.
05-12-2011, 11:34 AM   #11
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Save yourself the trouble and ebay the konica lens, while you are doing that, get yourself another... ->

http://cgi.ebay.com/Vivitar-28mm-f-2-8-Wide-Angle-Lens-K-Mount-EX-/170640492...ht_1337wt_1139
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